Rear swing arm suspension system for a motorcycle

ABSTRACT

The object of this invention is to provide a one-sided rear swing arm suspension system for a motorcycle having a chain-driven rear wheel, in which the tension of the drive chain may be adjusted without affecting the ride height of the motorcycle. The suspension system includes a rear swing arm (10) that is pivotably attached to the body (12) of the motorcycle, and which extends rearwardly around and alongside the rear wheel (16). The rear end of the swing arm includes elongate recesses which guide and receive an adjustment yoke (18). The rear wheel is journalled on a spindle (28) that extends transversely from the adjustment yoke. The yoke is positionable longitudinally on the swing arm by means of an adjustment stud (22) extending from the swing arm, and a corresponding adjustment nut (24) entrapped in the neck of the yoke. A single adjustment clamp nut (30) on the end of the spindle operates to secure the spindle to the yoke and to also secure the yoke to the swing arm at a selected position corresponding to a desired chain tension.

TECHNICAL FIELD

The invention described and claimed herein is generally related tomotorcycle frame and suspension construction. More particularly, thepresent invention is related to swing-arm suspension systems for therear wheel of a motorcycle.

BACKGROUND ART

For over thirty years motorcycles have typically included forked rearswing arm suspension systems. In such systems the rear wheel isjournalled to the end of a forked swing arm. The forward end of theswing arm is hinged to the motorcycle body at a point forward of thewheel, and extends rearwardly therefrom. The swing arm is spring-loadedand damped, so as to absorb weight loads and road shocks by undergoinglimited swinging motion in a vertical plane.

Some touring motorcycles have a pair of spring-loaded shock absorberswhich extend upwardly from the ends of the forked swing arm. In suchsystems weight loads and road shocks are transmitted almost directlyfrom the wheel axle to the shock absorbers. Most modern motorcycles,however, particularly including the off-road, or "motocross"motorcycles, have a single shock absorber and spring assembly, which islocated forward of the wheel. In such systems weight loads and roadshocks are transmitted through the swing arm to the shock absorber.

In recent years there has been introduced at least one class ofone-sided rear swing arm assemblies. In these assemblies the rear wheelis journalled to an axle that extends horizontally in a cantileveredmanner from the end of the swing arm, with the swing arm extendingaround and alongside one side of the wheel. Such an arrangementfacilitates changing of the rear wheel, which can be removedhorizontally from the free end of the axle, and also results in lighteroverall weight, greater rigidity, and other advantages.

A problem associated with the previously known one-sided rear swing armassemblies is that it has been difficult to provide a satisfactorymechanism for adjusting the tension in the drive chain. It will berecognized that in conventional forked swing arm assemblies this is nota problem, as the chain tension is readily adjusted by sliding the wheelforwardly or rearwardly in the slots which are ordinarily employed forengaging and supporting the axle of the wheel, and which are elongatedfor the purpose of allowing for adjustment of the chain tension.However, in the one-sided swing arm assemblies this approach has notbeen feasible.

Consequently, one approach has been to journal the rear wheel in aneccentrically mounted journal bearing, which can be selectively rotatedto adjust the chain tension. Although this mechanism accomplishes thepurpose of adjusting the chain tension, it also necessarily results inthe rear wheel being raised or lowered with respect to the rest of themotorcycle, resulting in a small but definite change in ride height whenthe chain tension is adjusted.

The applicant has previously disclosed and claimed a one-sided frontwheel suspension system in his U.S. Pat. No. 4,526,249, issued on Jul.2, 1985, which is hereby incorporated by reference. As will beappreciated from the description below of the present invention, some ofthe same advantages that are obtained in the one-sided front wheelsuspension system are also obtained in the rear wheel suspension systemof the present invention. For example, in a one-sided suspension systemweight loads and road shocks are transmitted to points on the motorcyclebody which are both low, that is, close to the ground, and close to thecenter of gravity of the motorcycle, with consequent improvement in thehandling, performance and ride of the motorcycle. Also, in a one-sidedsuspension system weight loads and road shocks are transmitted in a moredirect path to the motorcycle body, thereby permitting a net reductionin the size and weight of the load-bearing structures that transmitthese loads to the motorcycle body.

DISCLOSURE OF INVENTION

Accordingly, it is the object and purpose of the present invention toprovide a one-sided rear swing arm suspension for a motorcycle having achain-driven rear wheel.

More particularly, it is an object and purpose of the present inventionto provide a one-sided rear swing arm suspension which enables thetension in the drive chain to be adjusted without resulting in verticaldisplacement of the rear wheel relative to the body of the motorcycle,and thereby without affecting the ride height of the motorcycle.

The foregoing objects and purposes are attained in the presentinvention, which provides a one-sided rear swing arm suspension systemfor a motorcycle having a body and a rear wheel which is driven by adrive chain. The suspension system includes a rear swing arm, anadjustable yoke and associated adjustment means, and a spindle. The rearwheel is journalled to the spindle. The spindle extends from the yoketransversely with respect to the swing arm. The yoke is adjustablysecured to the swing arm by the adjustment means.

The swing arm includes first and second ends. The first end of the swingarm is pivotably attached to the body of the motorcycle at a positionforward of the rear wheel, and ordinarily at a height correspondinggenerally to the axle height of the rear wheel. The swing arm extendsrearwardly from the pivotably attached first end, around and alongsidethe rear wheel, to its second end. The second end of the swing armincludes longitudinal guide means for slidably receiving thereon theadjustable yoke. The yoke includes cooperable longitudinal guide meanswhich engage the guide means on the second end of the swing arm. Theguide means of the swing arm and the guide means of the yoke engage oneanother so as to allow selective longitudinal positioning of the yoke onthe swing arm, while at the same time preventing relative rotationaldisplacement of the yoke about the swing arm when the yoke is secured tothe swing arm by the adjustment means.

The adjustable yoke preferably includes inner and outer side memberswhich enclose the second end of the swing arm and which are slidablyengaged by the guide means provided on the second end of the swing arm.The spindle extends from the yoke transversely with respect to the swingarm. The adjustment means enables selectively positioning the yokelongitudinally along the second end of the swing arm and also rigidlysecures the yoke to the second end of the swing arm, preventing anylongitudinal or rotational displacement of the yoke relative to theswing arm once the yoke is so secured. The adjustment means enables thedistance of the yoke from the motorcycle body, and thus also thedistance of the associated spindle from the body, to be selectivelyadjusted to thereby permit adjustment of the tension in the drive chain.

In a preferred embodiment the yoke includes coaxial transverse boresthrough both of its aforementioned side members; and the second end ofthe swing arm, on which the yoke is received, has an elongatelongitudinal slot, through which the axes of the coaxial bores extend.The spindle passes through the bores of the yoke and also through theelongate slot in the swing arm. The spindle includes an integralshoulder which abuts the inside side member of the yoke, and is securedby means of an adjustment clamp nut on the opposite side. When theadjustment clamp nut is tightened, the spindle is firmly secured to theyoke, and the yoke is at the same time rigidly clamped about the secondend of the swing arm, thereby securing the yoke and spindle at a desireddistance from the motorcycle body.

The second end of the swing arm preferably includes a longitudinallyextending adjustment stud, which extends rearwardly from the second endof the swing arm through a bore in the yoke. The yoke preferably alsoincludes a rotatable, captured adjustment nut which engages theadjustment stud and which permits selective positioning of the yoke onthe second end of the swing arm. With this arrangement the yoke ispositioned with the adjustment nut, and subsequently secured to theswing arm with the adjustment clamp nut.

These and other aspects of the invention will be more fully apparentupon consideration of the following detailed description of a preferredembodiment, when taken with the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings constitute part of this specification and arehereby incorporated by reference. In the drawings:

FIG. 1 is rear quarter view of a motorcycle equipped with the one-sidedrear swing arm suspension system of the present invention;

FIG. 2 is an exploded isometric view of the one-sided rear swing armsuspension system shown in FIG. 1;

FIG. 3 is a rear end view, taken along line 3--3 of FIG. 2, of the swingarm of the suspension system illustrated in FIGS. 1 and 2; with theyoke, spindle and other elements of the suspension system removed;

FIG. 4 is a front end view, taken along line 4--4 of FIG. 2, of theadjustable yoke of the suspension system shown in FIGS. 1 and 2, withits associated adjustment mechanism removed;

FIG. 5 is a side view of the assembled suspension system of FIGS. 1 and2;

FIG. 6 is a plan view in cross section, taken along section line 6--6 ofFIG. 7, of the assembled suspension system of FIGS. 1, 2 and 5; and

FIG. 7 is a rear end view in cross section, taken along section line7--7 of FIG. 6, of the assembled suspension system of FIGS. 1, 2 and 5.

BEST MODE FOR CARRYING OUT THE INVENTION

Referring to FIGS. 1 through 7, and beginning particularly with FIG. 1,there is illustrated a motorcycle provided with a one-sided rear swingarm suspension system that constitutes a preferred embodiment and thebest mode contemplated for carrying out the present invention. Thesuspension system generally includes a one-sided rear swing arm 10,which extends generally horizontally and rearwardly from the body 12 ofthe motorcycle. The forward, or first, end 10a of the swing arm 10 ispivotably attached to the motorcycle body 12 by means of an elongatebearing shaft 14. The swing arm 10 is pivotable about the bearing shaft14 in a vertical plane. The swing arm 10 is spring-loaded so as toextend approximately horizontally from the body 12 of the motorcycle,and at a height corresponding approximately to the axle height of therear wheel 16, under normal weight loads and operating conditions. Theswing arm 10 is flared to a maximum width at its forward end 10a, so asto distribute twisting loads on the swing arm 10 over the full length ofthe bearing shaft 14, and to thereby provide maximum torsional rigidityto the swing arm 10. The flared forward end 10a of the swing arm 10includes a large central hole 10b, through which a sprung and dampedshock absorber assembly (not shown) ordinarily extends. The shockabsorber assembly will normally be attached to a mounting boss (notshown) that extends from the underside of the swing arm 10 so as to becentered beneath the hole 10b. The shock absorber assembly forms no partof the present invention and consequently will not be described further.

It will be appreciated that in contemporary motorcycles there is anincreasing tendency to integrate structural elements of the frame andthe engine into an integrated unit that attains optimum structural,weight and performance characteristics. Consequently, for the purposesof this description, it should be understood that the body 12 maygenerally include a frame, or the engine of the motorcycle, or anintegrated combination of the engine, frame and/or other majorstructural elements. In this regard the body 12 thus consists of themajor structural components to which the swing arm 10 is attached.

From the flared forward end 10a, the swing arm 10 curves outwardly andextends along the left side of the rear wheel 16. The swing arm 10 is arectangular tube along the majority of its length, and is welded to asolid spindle boss 10c which forms the second, or rear, end of the swingarm 10. In the preferred embodiment the spindle boss 10c thusconstitutes the second end of the swing arm 10. The spindle boss 10c isadapted to slidably receive a cooperable adjustment yoke 18. Briefly, asdescribed further below, the spindle boss 10c and the cooperableadjustment yoke 18 operate to enable the wheel 16 to be securelyjournalled to the end of the swing arm 10, while also enabling thetension in a main drive chain 20 to be adjusted to a desired level.

Referring particularly to FIGS. 2 and 3, the spindle boss 10c on therear end of the swing arm 10 is generally rectangular in cross section,and includes a pair of elongate, rearwardly opening inner and outerguide recesses 10d and 10e, respectively, which are formed in theopposite side walls of the boss 10c. The recesses 10d and 10e includefloor surfaces 10f and 10g, respectively, which are parallel to oneanother and which are also generally vertical in orientation andparallel to the side walls of the swing arm 10. The recesses 10d and 10efurther include side walls 10h and 10i, respectively, which extend atapproximately 45 degree angles with respect to the floors 10f and 10g ofthe recesses 10d and 10e, as well as with respect to the sides of thespindle boss 10c and the swing arm 10 itself. The boss 10c furtherincludes an elongate adjustment slot 10j which provides a transverseopening through the boss 10c. The adjustment slot 10j is generallycentered in the recesses 10d and 10e and extends longitudinally, orparallel to the longitudinal axis of the swing arm 10. An adjustmentstud 22 extends rearwardly from the rear end surface of the boss 10c.

The adjustment yoke 18 is generally U-shaped and includes generallyplanar, integral inner and outer side members 18a and 18b, respectively.The integral side members 18a and 18b have inwardly facing edge surfaces18c and 18d, respectively, which extend at an angle of approximately 45degrees with respect to the planes of the side members 18a and 18b. Whenthe yoke 18 is slid onto the swing arm boss 10c, the angled edgesurfaces 18c and 18d slidably oppose the corresponding angled side walls10h and 10i, respectively, of the spindle boss 10c. It will be seenfurther that the yoke 18 is sized so that the side members 18a and 18bare slidable longitudinally within the guide recesses 10d and 10e of thespindle boss 10c.

The neck of the yoke 18 includes a centered bore 18e (FIG. 4), in whichthere is located an entrapped position adjustment nut 24. The entrappednut 24 includes a tubular sleeve 24a, which is threaded on its insidesurface so as to engage the adjustment stud 22. An integral shoulder 24bon the inside end of the sleeve 24a, together with a peened or weldednut 24c on the outer end of the sleeve 24a, retain the sleeve 24a withinthe bore 18e. The nut 24 rotates freely in the bore 18e of the yoke 18,but is constrained against axial displacement within the bore 18e,thereby enabling the yoke 18 to be adjustably positioned on the spindleboss 10c by rotating the adjustment nut 24 while engaged with theadjustment stud 22 until a desired position of the yoke 18 is obtainedwith respect to the boss 10c. As will be seen below, this is how thechain tension in drive chain 20 is adjusted. A locking nut 26, alsoengaged on stud 22 outside the yoke 18, so as to abut the entrappedposition adjustment nut 24, enables the yoke 18 to be locked into adesired position with respect to the spindle boss 10c.

The yoke 18 further includes an inner spindle bore 18f, which passesthrough inner side member 18a; and an outer spindle bore 18g, whichpasses through the outer side member 18b. The spindle bores 18f and 18gare coaxial, and are positioned so that they are centered on theadjustment slot 10j when the yoke 18 is slipped onto the swing arm boss10c. As the yoke 18 is moved forwardly or rearwardly on the boss 10c,the spindle bores 18f and 18g move along the axis of the slot 10j whileremaining centered on the slot 10j.

The wheel 16 is journalled on a spindle 28, in a manner furtherdescribed below. The spindle 28 generally includes a large-diameterouter end 28a, which passes through the yoke 18, and a generally taperedinner end 28b, on which the wheel 16 is journalled. The outer spindleend 28a passes through both bores 18f and 18g of the yoke 18, and alsopasses through the adjustment slot 10j of the spindle boss 10c. Theouter end 28a of the spindle 28 is sized so as to be press fitted intothe inner bore 18f (being so fitted while the yoke 18 is positioned onthe spindle boss 10c, so that the inner end 28a of the spindle 28 passesthrough the adjustment slot 10j), and is slip fitted through bore 18g.An integral annular shoulder 28c on the spindle 28 abuts the inner sidemember 18a and thereby limits the penetration of the spindle 28 throughthe yoke 18. The portion of the outer spindle end 28a passing throughand extending from the outer bore 18g is threaded, so as to beengageable with an adjustment clamp nut 30.

It will be noted that the 45 degree side walls 10h and 10i of thespindle boss 10c abut the corresponding 45 degree edge surfaces 18c and18d of the yoke 18. When the adjustment clamp nut 30 is loosened, thesesurfaces slide past one another as the position of the yoke 18 on theswing arm boss 10c is adjusted. When the adjustment clamp nut 30 istightened, these surfaces are driven against one another. Thisarrangement results in the spindle 28 being self-centered in the slot10j, and also results in the spindle 28 being secured against both axialas well as radial displacements with respect to the end of the swing arm10 and the boss 10c. This results in exceptionally secure and stablepositioning of the spindle 28, while nevertheless allowing forlongitudinal adjustment of the position of the spindle 28 along theswing arm boss 10c.

A chain sprocket 32 and an associated sprocket carrier 34 are journalledto the spindle 28 directly adjacent to and slightly spaced from the yoke18. The sprocket 32 is bolted to the sprocket carrier 34 by means ofbolts 36 and associated nuts. The sprocket carrier 34 is journalled tothe spindle 28 by means of a bearing 38. The sprocket 32 is aligned witha transmission drive sprocket (not shown) which is located near the rearof the motorcycle body, and is connected to the transmission drivesprocket by the drive chain 20.

Adjacent to the sprocket carrier 34, and also journalled on the spindle28, is a wheel carrier 40. The wheel carrier 40 supports severalelements. First, the wheel 16 is bolted to the wheel carrier 40 by meansof wheel bolts 42. Secondly, the wheel carrier 40 supports a brake disk46, which is secured to the wheel carrier by bolts 48. The wheel carrier40 also includes five integral, cylindrical drive elements 49, whichextend into the sprocket carrier 34 and which engage cooperablypositioned rubber drive cushions 50. The drive cushions 50 are annularin shape and are set into cooperably shaped circular recesses in thesprocket carrier 34. The drive cushions 50 operate to cushion the drivetrain link between the sprocket carrier 34 and the wheel carrier 40.

The wheel carrier 40 is journalled to the spindle 28 by means of a pairof outer and inner bearings 52 and 53, respectively. The wheel carrier40 is secured to the spindle 28 by means of a spindle nut 54.

The swing arm 10 further includes an integral brake mounting boss 56,which extends inwardly from the inner side of the swing arm 10 at aposition just inside the rim of the rear wheel 16. A caliper bracket 58is attached to the brake mounting boss 56. The caliper bracket 58extends downwardly and rearwardly from the boss 56, adjacent the wheel16. A brake caliper 60 is affixed to the end of the bracket 58, and ispositioned so as to straddle the outer periphery of the brake disk 46.

As noted above, the tension in the drive chain 20 is adjusted by slidingthe yoke 18 forwardly or rearwardly on the swing arm boss 10c. Inoperation, the yoke 18 is first positioned longitudinally along the boss10c by turning the adjustment position nut 24, with the clamp nut 30being loosened just sufficiently to permit sliding displacement of theyoke 18 and spindle 28 with respect to the swing arm boss 10c. Theadjustment nut 24 is turned with the clamp nut 30 loosened in thismanner until a desired tension is attained in the drive chain 20. Theadjustment clamp nut 30 is then tightened on the spindle 28, and thelocking nut 26 is tightened on the stud 22. Tightening of the clamp nut30 clamps the yoke side members 18a and 18b about the opposite sides ofthe swing arm boss 10c and thereby securely affixes the yoke 18 to thespindle boss 10c, at the position previously selected by means of theadjustment position nut 24. It will noted that adjustment of the chaintension in this manner has no effect on the vertical position of thespindle 28 with respect to the end of the swing arm 10, and thus has noeffect on the ride height of the motorcycle.

The one-sided swing arm suspension system of the present invention maybe sprung and damped by any one of a number of conventional shockabsorber mechanisms of the general type previously used for forked swingarm suspensions. The preferred embodiment of the invention describedabove is adapted to receive a shock absorber that extends through thehole 10b in the swing arm 10. Such a shock absorber would be attached atits upper end to the body of the motorcycle, and would be attached atits lower end to a boss or bracket affixed to the swing arm 10 andpositioned beneath the hole 10b. Other suitable shock absorptionsystems, which may be known in the art, may however also be employed.

Industrial Applicability

The present invention provides a one-sided rear wheel suspension in amotorcycle, wherein the drive chain tension may be adjusted withoutaffecting the ride height of the motorcycle. This combinationfacilitates changing of the rear wheel while also ensuring a uniformride height and uniform response to weight loads and road shocksregardless of adjustments made to the chain tension. Further, thespindle 28 is a non-rotating part, thus reducing slightly the rotatingmass of the wheel assembly.

Although the present invention is described herein with reference to apreferred embodiment, it will be understood that various modifications,substitutions and alterations, which may be apparent to one of ordinaryskill in the art, may be made without departing from the essentialinvention. Accordingly, the scope of the patent protection claimedherein is defined solely by the following claims.

The embodiments of the invention in which patent protection is claimedare as follows:
 1. A one-sided rear swing arm suspension system for amotorcycle, said motorcycle having a body and a rear wheel, said rearwheel having a sprocket which is driven by a drive chain, comprising:arear swing arm pivotably attached to said body of said motorcycle, saidswing arm including longitudinal guide means for slidably receiving anadjustable yoke and a longitudinal adjustment slot passing transverselytherethrough; an adjustable U-shaped yoke having guide means forslidably engaging said guide means of said swing arm; a non-rotatingaxle spindle on which said rear wheel and its associated sprocket arejournalled, said spindle passing through said longitudinal adjustmentslot and extending from said adjustable yoke transversely with respectto said swing arm; and adjustment means operable to adjustably securesaid yoke to said swing arm at a selected longitudinal position alongsaid swing arm by clamping said U-shape yoke along said axle spindle tosaid swing arm, whereby said wheel and said sprocket may be journalledto said spindle at a selected distance from said body of saidmotorcycle, and whereby the tension in said drive chain may be therebyadjusted without affecting the ride height of the motorcycle.
 2. Theone-sided rear swing arm suspension system defined in claim 1 whereinsaid swing arm has first and second ends, said first end of said swingarm being pivotably attached to said body of said motorcycle forward ofsaid wheel, said swing arm extending from said first end around andalongside said rear wheel to said second end, said second end of saidswing arm including longitudinal guide means for slidably receivingthereon said adjustable yoke, said yoke including inside and outsideside members engageable with said guide means of said second end of saidswing arm, said side members of said yoke including cooperable boresthrough which said spindle extends, and wherein said guide means of saidswing arm and said side members of said yoke operate to prevent relativerotational displacement of said yoke and said spindle with respect tosaid swing arm when said yoke is secured to said swing arm.
 3. Aone-sided rear swing arm suspension system for a motorcycle having abody and a rear wheel driven by a drive chain, said suspension systemcomprising:a rear swing arm pivotably attached to said body of saidmotorcycle and extending rearwardly along one side of said rear wheel,said swing arm including a rear end having an inner side and an outerside, and said rear end of said swing arm further including alongitudinal adjustment slot passing transversely therethrough; aU-shaped yoke having inner and outer side members slidably engageablewith said swing arm along said inner and outer sides respectively ofsaid rear end of said swing arm; a non-rotating axle spindle on whichsaid rear wheel is journalled, said axle spindle connecting said sidemembers of said yoke and passing through said adjustment slot in saidrear end of said swing arm and extending from said inner side member ofsaid yoke transversely with respect to said swing arm, and means forcompressing said side members of said yoke along said axle spindle so asto clamp said yoke to said inner and outer sides of said rear end ofsaid swing arm; and chain adjustment means operable to adjustablyposition said yoke along said rear end of said swing arm at selectedlongitudinal positions, whereby the tension in said drive chain may beadjusted.
 4. The one-sided rear swing arm suspension system defined inclaim 3 wherein said inner and outer sides of said rear end of saidswing arm include longitudinal guide means for slidably receivingthereon said inner and outer side members, respectively, of said yoke,whereby said yoke is slidably adjustable in longitudinal position onsaid rear end of said swing arm, and wherein said guide means of saidswing arm operate to prevent relative rotational displacement of saidyoke with respect to said swing arm when said yoke is secured to saidswing arm.
 5. The one-sided rear swing arm suspension system defined inclaim 4 wherein a first end of said axle spindle is threaded and extendsthrough bores in said inner and outer side members of said yoke, andwherein said spindle further includes an integral annular shoulder whichabuts the outer side of said inner side member of said yoke, and whereinsaid means for compressing said side members of said yoke along saidaxle spindle comprises an adjustment clamp nut threaded to said firstend of said axle spindle, whereby tightening of said adjustment clampnut causes said side members of said yoke to clamp said rear end of saidswing arm.
 6. The one-sided rear swing arm suspension system defined inclaim 5 wherein said chain adjustment means comprises an adjustment studextending rearwardly from said rear end of said swing arm, and whereinsaid yoke includes a central bore having retained therein an entrappedrotatable adjustment position nut engageable on said adjustment stud,whereby the position of said yoke and spindle with respect to said swingarm and said motorcycle body are selectively adjustable by rotating saidadjustment position nut.
 7. The one-sided rear swing arm suspensionsystem defined in claim 5 wherein said guide means on said rear end ofsaid swing arm comprises a pair of inner and outer, rearwardly openingelongate recesses, said recesses having side walls which extend at anacute angle with respect to the axis of said spindle, and wherein saidside members of said yoke have edge surfaces which extend at acorresponding acute angle with respect to the axis of said spindle,whereby tightening of said adjustment clamp nut causes said side wallsand said edge surfaces to abut and thereby center and secure saidspindle against axial as well as radial displacements.
 8. The one-sidedrear swing arm suspension system defined in claim 5 wherein said rearend of said swing arm includes a spindle boss affixed to said swing arm,and wherein said guide means on said rear end of said swing arm comprisea pair of inner and outer, rearwardly opening elongate recesses formedin said spindle boss, said recesses having side walls which extend at anacute angle with respect to the axis of said spindle, and wherein saidside members of said yoke have edge surfaces which extend at acorresponding acute angle with respect to the axis of said spindle,whereby tightening of said adjustment clamp nut causes said side wallsand said edge surfaces to abut and thereby center and secure saidspindle against axial as well as radial displacements.
 9. The one-sidedrear swing arm suspension system defined in claim 8 wherein said acuteangles of said side walls of said elongate recesses and said edgesurfaces of said side members extend at approximately forty five degreeswith respect to the axis of said axle spindle.
 10. The one-sided rearswing arm suspension system defined in claim 3 further comprising asprocket carrier and a wheel carrier each journalled to said spindle,said sprocket carrier being journalled to said spindle adjacent saidyoke and supporting a chain sprocket, and said wheel carrier beingjournalled to said spindle adjacent said sprocket carrier and on theopposite side of said sprocket carrier from said yoke.
 11. The one-sidedrear swing arm suspension system defined in claim 10 wherein saidsprocket carrier is engaged with said wheel carrier through a pluralityof cushion elements contained in said sprocket carrier.
 12. Theone-sided rear swing arm suspension system defined in claim 11 whereinsaid wheel carrier supports a brake disk, and wherein said swing armfurther comprises a brake mounting boss, and a brake caliper mounted tosaid mounting boss and positioned to engage said brake disk.
 13. Theone-sided rear swing arm suspension system defined in claim 3 whereinsaid swing arm is generally a rectangular tubular arm, and wherein saidrear end of said swing arm comprises a spindle boss includinglongitudinal inner and outer guide means, said spindle boss furthercomprising an adjustment stud extending rearwardly therefrom, and wheresaid yoke includes an entrapped position adjustment nut engageable withsaid stud, whereby said yoke may be selectively positionedlongitudinally on said spindle boss.
 14. The one-sided rear swing armsuspension system defined in claim 13 wherein said side members of saidyoke include coaxial transverse bores through which said spindleextends, and wherein a first end of said spindle is press fitted throughsaid bore of said inside side member of said yoke, and wherein saidspindle is slip fitted through said bore of said outside side member ofsaid yoke, said spindle including an integral shoulder which limits thepenetration of said spindle through said bore of said inside sidemember, and wherein said spindle and said yoke are fixedly secured tosaid spindle boss by means of an adjustment clamp nut threaded to saidfirst end of said spindle extending through said outer side member ofsaid yoke, said adjustment clamp nut operating to clamp said sidemembers of said yoke about said spindle boss while also centering andsecuring said spindle to said swing arm.
 15. A one-sided rear swing armsuspension system for a motorcycle having a body and a rear wheel drivenby a drive chain, said suspension system comprising:a rear swing armpivotably attached to said body of said motorcycle and extendingrearwardly along one side of said rear wheel, said swing arm including arear end having an inner side and an outer side, and said rear end ofsaid swing arm further including a longitudinal adjustment slot passingtransversely therethrough; a U-shaped yoke having inner and outer sidemembers slidably engageable with said swing arm along said inner andouter sides respectively of said rear end of said swing arm; anon-rotating axle spindle on which said rear wheel is journalled, saidaxle spindle connecting said side members of said yoke and passingthrough said adjustment slot in said rear end of said swing arm andextending from said inner side member of said yoke transversely withrespect to said swing arm; and means for compressing said side membersof said yoke along said axle spindle so as to clamp said yoke to saidinner and outer sides of said rear end of said swing arm; whereby saidyoke and said axle spindle may be positioned and secured at selectedpositions along the rear end of the swing arm so as to enable selectiveadjustment of the tension in the drive chain.
 16. The one-sided rearswing arm suspension system defined in claim 15 wherein said inner andouter sides of said rear end of said swing arm include longitudinalguide means for slidably receiving thereon said inner and outer sidemembers, respectively, of said yoke, whereby said yoke is slidablyadjustable in longitudinal position along said rear end of said swingarm, and wherein said guide means of said swing arm operates to preventrelative rotational displacement of said yoke with respect to said swingarm when said yoke is secured to said swing arm.
 17. The one-sided rearswing arm suspension system defined in claim 15 further comprising chainadjustment means including an adjustment stud extending rearwardly fromsaid rear end of said swing arm, and wherein said yoke includes acentral bore having retained therein an entrapped rotatable adjustmentposition nut engageable on said adjustment stud, whereby the position ofsaid yoke and spindle with respect to said swing arm and said motorcyclebody are selectively adjustable by rotating said adjustment positionnut.
 18. The one-sided rear swing arm suspension system defined in claim15 wherein said guide means on said rear end of said swing arm comprisesa pair of inner and outer, rearwardly opening elongate recesses, saidrecesses having side walls which extend at an acute angle with respectto the axis of said spindle, and wherein said side members of said yokehave edge surfaces which extend at a corresponding acute angle withrespect to the axis of said spindle, whereby compression of said sidemembers of said yoke along said axle spindle causes said side walls andsaid edge surfaces to abut in wedging relationship so as to therebycenter and secure said spindle with respect to said swing arm.
 19. Theone-sided rear swing arm suspension system defined in claim 15 wherein afirst end of said axle spindle is threaded and extends through saidinner and outer side members of said yoke, and wherein said axle spindlefurther includes an integral annular shoulder which abuts the outer sideof said inner side member of said yoke, and wherein said means forcompressing said side members of said yoke along said axle spindlecomprises an adjustment clamp nut threaded to said first end of saidspindle, whereby tightening of said adjustment clamp nut causes saidside members of said yoke to clamp said rear end of said swing arm whilealso centering and securing said axle spindle with respect to said swingarm.
 20. The one-sided rear swing arm suspension system defined in claim15 further comprising a sprocket carrier and a wheel carrier eachjournalled to said spindle, said sprocket carrier being journalled tosaid spindle adjacent said yoke and supporting a chain sprocket, andsaid wheel carrier being journalled to said spindle adjacent saidsprocket carrier and on the opposite side of said sprocket carrier fromsaid yoke.